Pac Versions [1/2]

Write Pac version to build.prop with inital gen script.

We really need a uniform system for Pac Versioning and this will make
it (easier) more fluid for us to make that version human readable in the
Rom (Settings->Info).

Our Pac major version are/have been;  "23.0.0" (2 versions), 4.4, 4.3,
4.4.4, 4.4.4, 4.4, M1, Build 1.
Our minor verions are/have been; Build 1, Alpha 1, (none), RC-1,
Beta 1.0, release, RC1, RC.

Change-Id: Ie47a4c2b8dad18cc3794d73fc59cd4455902fa70